The reestablishment of productive forests over mining waste and overburden is a primary reclamation goal in oil sands mining in Northern Alberta, Canada. Soil water conditions in coarse-textured soils can be limiting to forest growth. The objective of this study was to evaluate the effect that textural variability may have on plant-available water and concomitant forest productivity on coarse-textured reclamation soils. The ecophysiological and biogeochemical processes model, Biome-BGC (Thornton et al., Agricultural and Forest Meteorology 113: 185–222, 2002), was employed to simulate forest dynamics. The water flow sub-model in Biome-BGC was replaced by a field-validated physically based formulation for transient unsaturated water flow. The modified model was assessed using validated physiological parameters, and model predictions were compared with measurements of aboveground biomass dynamics for jack pine (Pinus banksiana Lamb), white spruce [Picea glauca (Moench) Voss], and trembling aspen (Populus tremuloides Michx.). The modified Biome-BGC model was then used to evaluate the response of leaf area index and net primary production to available water holding capacity on texturally variable, coarse-textured soils. The results indicate that textural variability could increase the available water holding capacity within a 1-m profile of coarse-textured soil by 8 to 16 mm. This enhanced available water holding capacity could increase forest leaf area index by 0·3 to 0·8 and net primary production by 14–30% depending on the specific soil texture and tree species. Copyright © 2012 John Wiley & Sons, Ltd.